PROJECT SUMMARY Cancer-related fatigue (CRF) is the most commonly reported side effect of cancer treatment and is defined by the National Comprehensive Cancer Network as ?a distressing, persistent, subjective sense of physical, emotional, and cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity.? Such fatigue is often associated with sleep problems, depression, quality of life, and agitation. Unfortunately, currently available interventions for CRF are, at best, only modestly effective. Pharmacological agents have been studied for CRF, but there is insufficient evidence to recommend their use. Non-pharmacological interventions have shown clinical benefit, but they can be labor-intensive, expensive, and cumbersome for patients. The light therapy to be studied incorporates systematic exposure to bluish-white light is hypothesized to entrain circadian rhythms, which play a crucial role in the cellular and physiological functions of the brain and body. Indeed, disruption of these rhythms has been shown to affect sleep quantity and quality, depression, and fatigue among cancer patients. The proposed research will explore the acceptability, feasibility and potential efficacy of systematic programmed light illumination (sPI) exposure to prevent CRF in patients undergoing autologous stem cell transplantation in the treatment of Multiple Myeloma, as provided during their inpatient hospital stay for approximately two weeks following infusion of stem cells. sPI will deliver appropriately timed ambient, low-level, bluish-white light to patients during their hospital stay with floor lamps designed to deliver high circadian stimulation over the course of the day. Participants will be randomized to one of two treatment conditions: one with an active intervention, and one with a non-active comparison. During inpatient hospitalization, sPI will consist of: high intensity (400 lux) during morning hours (6AM to 10AM), followed by a decrease in intensity (lower than 50 lux) during late morning to early evening hours (10AM to 6PM), and no sPI at night (6PM to 6AM). The non-active comparison condition will consist of less than 20 lux blue-white light during 6AM-6PM period and no light from 6PM-6AM. The proposed research will address three specific aims: 1) Determine if sPI results in significant prevention/reduction of the development of CRF, depression, sleep problems, circadian rhythm disruption and diminished quality of life compared to the comparison light condition. 2) Explore whether the effects of sPI on CRF are mediated by changes in sleep, depressive symptoms, circadian activity rhythms, and/or melatonin 3) Determine the feasibility and acceptability of sPI, actigraphy, urine collection and monitoring of light exposure.